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Full text of "Circuits"

Control a Servo Motor Without Programming 



MakejProjects 



Control a Servo Motor Without 
Programming 

Written By: Jonathan Best 



TOOLS: 

Fume extractor (1) 
Heatproof mat (1) 
Soldering iron (1) 



SUMMARY 

I am going to guide you through the process of making a circuit that will allow you to control 
a servo by turning a dial. At the same time I will explain what is going on in the circuit and 
how it works. 



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Control a Servo Motor Without Programming 



Step 1 — Control a Servo Motor Without Programming 



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• A servo motor is controlled by sending a series of pulses to it. This is called "pulse width 
modulation." Depending on the length of the pulse it will turn to a specific angle. 

• A pulse must be sent to the servo every 20 milliseconds. The pulse length will vary from 
0.5ms to 2ms. If it is 0.5ms the servo will turn as far as it can anti-clockwise. If it is 2ms it 
will turn as far as it can clockwise. 

• By using a pulse-generating circuit controlled by a potentiometer any pulse length between 
0.5ms and 2.0ms can be sent to the servo. This allows us to move the servo arm to any 
position desired. 



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Control a Servo Motor Without Programming 



Step 2 









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555 timer 

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• To create these pulses we are going to use a 555 timer circuit. 

• There are two types of 555 timer circuits, astable and monostable. For this project we will 
be using an astable circuit. This means that it will continually send pulses as long as it has 
power. 

• The circuit uses a 555 timer chip, with capacitors and resistors controlling the timing. For 
this circuit we will be using the NE555. 



Step 3 




• This is the circuit diagram for the 
servo controller. You can either 
make it on a PCB, on veroboard, or 
on a breadboard. 

• Whichever you choose you should 
always breadboard it first. This lets 
you check that you have all the 
right components and the correct 
layout. 



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Control a Servo Motor Without Programming 



Step 4 




• This is my circuit that I made. I made it on veroboard and everything is working fine. 

• A few tips to remember when using veroboard. 

• 1st; always drill through the track where your chip is BEFORE doing any soldering. 

• 2nd; always use a dill / chip mount to hold your chip. This prevents the chip from getting 
damaged when soldering. 

• 3rd; always pass leads through the board before soldering them in. This prevents them 
from getting damaged if pulled upon. 



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Page 4 of 4